Add continuous brushing for placed suspicious blocks

[tastybento]

Summary

• Suspicious gravel/sand are placed programmatically by the magic-block handler, so vanilla brush mechanics never run on them. Previously each right-click advanced one dust stage with no animation, forcing players to spam-click with no visual progress.
• Each click now also plays dust particles + brushing sound, and starts a 10-tick repeating session that keeps dusting while the player holds right-click (detected via Paper's Player#isHandRaised()). The session cancels when the player releases, looks away, swaps items, disconnects, or the block disappears — matching vanilla feel (~5s for a full brush).
• completeBrush was refactored from (PlayerInteractEvent, Block) to (Player, Block) so the timer task can call it directly.

Closes #490

Test plan

• mvn test -Dtest=BlockListenerTest2 — 39/39 pass
• In-game: reach a phase that yields a suspicious block, hold right-click with a brush — verify smooth dust progression with particles + sound, loot drops on completion, brush takes durability
• In-game: release mid-brush — verify dusting pauses; re-press to resume
• In-game: look away mid-brush — verify the session cancels

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud